Because of their widely ranging mechanical properties and their ability to be relatively easily machined and formed, polyurethane materials, such as urethane elastomers and foams, have found wide use in a multitude of industrial and consumer applications.
The production of urethane polymers is well known in the art. Urethanes are formed when isocyanate (NCO) groups react with hydroxyl (OH) groups. The most common method of urethane production is via the reaction of a petroleum-derived-polyol and an isocyanate, which forms the backbone urethane group. Polyester polyols and polyether polyols are the most common polyols derived from petroleum used in urethane production. Polyols are polyhydric alcohols, i.e., alcohols that contain two or more hydroxyl groups.
Sole use of polyols derived from petrochemicals such as polyester or polyether polyols in forming urethane products such as elastomers and foams is disadvantageous for a variety of reasons. Petrochemicals are ultimately derived from petroleum. Accordingly, the petrochemicals are a non-renewable resource. The production of a petroleum-derived polyol requires a great deal of energy, as oil must be drilled, extracted from the ground, transported to refineries, refined, and otherwise processed to yield the polyol. These efforts add to the cost of polyols and to the disadvantageous environmental effects of its production. Also, the price of petroleum-derived polyols tends to be somewhat unpredictable as it tends to fluctuate based on the fluctuating price of petroleum.
Also, as the consuming public becomes increasingly aware of environmental issues, there are distinct marketing disadvantages to petrochemical based products. Consumer demand for “greener” products continues to grow. As a result, it would be most advantageous to replace all or at least some of the polyester or polyether polyols, as used in the production of urethane polymers, with a more versatile, renewable, less costly, and more environmentally friendly component, such as vegetable oil-derived polyols.
One difficulty with the use of vegetable oil-derived polyols to produce a urethane product is that conventional methods of preparing polyols from vegetable oils, such as soybean oils, do not produce polyols having a significant content of hydroxyl groups. Accordingly, it would be advantageous to develop a method to produce vegetable oil-based polyols having increased reactive hydroxyl groups over conventional polyols derived from a vegetable oil such as blown vegetable oil.
Another difficulty with the use of vegetable oil-derived polyols to produce a urethane product is higher than desired residual acid values of the polyol, especially in blown soybean oil polyols (typical blown soybean oil-derived polyol, the residual acid value of a soybean oil-derived polyol ranges from about 5.4 mg KOH/gram to about 7.4 mg KOH/gram). Generally, in the production of urethane elastomers and foams, the residual acid present in vegetable oil-derived polyols retards isocyanate activity by interfering with the isocyanate/alcohol reaction. Also, where the catalyst used to produce urethane polymers is an amine, it is believed that the residual acid can neutralize the amine, making the catalyst less effective. Accordingly, it would be advantageous to develop a method to neutralize the residual acid of the polyol to form reactive hydroxy (OH) groups while not adversely impacting performance of the polyol. A lower acid vegetable oil-derived polyol would be desirable because the lower acid value would improve the performance of polyols in the production of urethane polymer, lower polyurethane catalyst requirements, and improve urethane physical properties due to improved polymer network formation. Accordingly, a significant need exists for low acid, higher functional polyols derived from vegetable oil, especially polyols derived from soybean oil, typically blown soybean oil, and a method for producing such lower acid, higher functional polyols.